The invention relates generally to the field of photography, and in particular to disposable single-use or one-time-use cameras. More specifically, the invention relates to a one-time use camera with a means to ensure film-on-sprocket retention during camera assembly.
Film and cameras that are all in one, commonly referred to as disposable single-use or one-time-use cameras, have become well known. The one-time-use camera is a simple point-and-shoot type camera comprising a conventional film cartridge within a cartridge receiving chamber in a main body part, an unexposed film roll prewound from the film cartridge onto a film supply spool within a film supply chamber in the main body part, a film-exposing backframe opening between the cartridge receiving and film supply chambers in the main body part, a fixed-focus taking lens, a film metering mechanism with a rotatably supported metering sprocket that has respective sprocket teeth for engaging the filmstrip at successive film perforations, a manually rotatable film winding thumbwheel coaxially engaged with a film winding spool inside the film cartridge, a single-blade shutter, a manually depressible shutter release button, an exposure counter wheel that has a numerical series of evenly spaced exposure count indicia and is incrementally rotated to successively view the exposure count indicia, an anti-backup pawl that engages the exposure counter wheel to prevent its reverse rotation, a direct see-through viewfinder having front and rear viewfinder lenses, and in some models an electronic flash. A pair of separate front and rear cover parts house the main body part between them to complete the camera. The rear cover part connects to the main body part and/or to the front cover part to make the main body part light-tight. A decorative cardboard outer box or label at least partially covers the front and rear cover parts and has respective openings for the taking lens, etc.
After each picture is taken with the one-time-use camera, the photographer manually rotates the thumbwheel in a film winding direction to similarly rotate the film winding spool inside the film cartridge. This winds an exposed frame of the filmstrip from the backframe opening into the film cartridge and advances an unexposed frame of the filmstrip from the unexposed film roll to the backframe opening. The rewinding movement of the filmstrip the equivalent of slightly more than one frame width rotates the metering sprocket in engagement with the filmstrip to decrement the exposure counter wheel to its next lower-numbered indicia and to pivot a metering lever into engagement with the thumbwheel in order to prevent further manual rotation of the thumbwheel in the film winding direction. Manually depressing the shutter release button to take another picture pivots the metering lever out of engagement with the thumbwheel to permit renewed rotation of the thumbwheel in the film winding direction. When the maximum number of exposures available on the filmstrip have been made and the filmstrip is completely wound into the film cartridge, the one-time-use camera is given to a photofinisher who separates the rear cover part from the main body part and removes the film cartridge with the exposed filmstrip from the cartridge receiving chamber. Then, he removes the exposed filmstrip from the film cartridge to develop the latent images and make prints for the customer.
During assembly of the one-time-use camera, an intermediate film section that longitudinally extends between the film winding spool in the film cartridge and the film supply spool is engaged with the metering sprocket via the sprocket teeth and the film perforations. Then, the rear cover part is connected to the main body part and/or to the front cover part to make the main body part light-tight. The rear cover part has several film guiding ribs that hold the intermediate film section engaged with the metering sprocket.
When the one-time-use camera is only partially assembled, i.e., before the rear cover part is connected to the main body part and/or to the front cover part, the intermediate film section between the film winding spool in the film cartridge and the film supply spool can retract out of engagement with the metering sprocket. This is because of the natural tendency of the film section to bow away from the metering sprocket and the ease with which the film cartridge can rotate in the film winding direction within the cartridge receiving chamber. If the film section disengages from the metering sprocket and is not re-engaged with the metering sprocket before the rear cover part is connected to the main body part and/or to the front cover part, the one-time-use camera will be inoperative.
The invention proposes a means to maintain film-on-sprocket retention during assembly of a one-time-use camera, i.e., before the rear cover part is connected to the main body part and/or to the front cover part.
According to one aspect of the invention, a partially assembled one-time-use camera comprising a film section that longitudinally extends from a rotatable film winding spool in a film cartridge and that is engaged with a rotatable metering sprocket, and a separate rear cover part that is to be placed over the film section and the film cartridge and is constructed to prevent the film section from retracting out of engagement with the metering sprocket, is characterized in that:
the film winding spool is rotatable in a film winding direction to wind the film section into the film cartridge, and the film section will retract out of engagement with the metering sprocket when the film cartridge is allowed to rotate in the film winding direction; and
a cartridge retention piece is positioned against the film cartridge to prevent the film cartridge from being rotated in the film winding direction when the rear cover part is not placed over the film section and the film cartridge, in order to prevent the film section from retracting out of engagement with the metering sprocket before the rear cover part is in place.
According to another aspect of the invention, a method of partially assembling a one-time-use camera, comprises:
placing a cartridge retention piece on top of a film cartridge to position a depending tab of the cartridge retention piece against a film passage snout of the film cartridge; and
engaging the cartridge retention piece with a main body part as the film cartridge is inserted into a chamber in the main body part, in order for the tab to prevent the film cartridge from being rotated within the chamber.
According to another aspect of the invention, a film delivering unit comprises:
a film cartridge including a cartridge shell, a rotatable film winding spool that is inside the cartridge shell and has a spool end portion that is accessible from outside the cartridge shell;
a film winding thumbwheel coaxially engaged with the spool end portion to rotate the film winding spool in a film winding direction; and
a cartridge retention piece between the film winding thumbwheel and the cartridge shell that is engageable to prevent rotation of the cartridge shell in the film winding direction when the film winding spool is rotated in that direction. Preferably, the cartridge shell has a film passage snout, and the cartridge retention piece has a tab against the snout to prevent the cartridge shell from being rotated in the film winding direction.